Fibrosis is characterized by excessive accumulation of collagen in the extracellular matrix of the involved tissue. It is a long-standing and challenging clinical problem for which no effective treatment is currently available. The production of collagen is a highly regulated physiological process, the disturbance of which may lead to the development of tissue fibrosis. The formation of fibrous tissue is part of the normal beneficial process of healing after injury. In some cases, however, an abnormal accumulation of fibrous material can severely interfere with the normal function of the affected tissue or even cause the complete loss of function of the affected organ.
A variety of compounds have been identified as anti-fibrosis agents via different mechanisms of action, including the suppression of collagen expression. For example, pantethine (D-bis-(N-pantothenyl-β-aminoethyl)-disulfide) has been reported to be effective for the inhibition of hepatic fibrosis (U.S. Pat. No. 4,937,266). Also, a hydrazine derivative, benzoic hydrazide, has been shown to be a powerful antifibrotic agent (U.S. Pat. Nos. 5,374,660 and 5,571,846). In addition, angiotensin inhibitors are used in combination with nitric oxide stimulators to inhibit the progression of fibrosis (U.S. Pat. Nos. 5,645,839 and 6,139,847). Further, A1 adenosine receptor antagonists and/or P2x purinoceptor antagonists are described for treating or preventing fibrosis and sclerosis (U.S. Pat. No. 6,117,445). More recently, somatostatin agonists, hepatocyte growth factors (HGFs), chymase inhibitors, and antagonists of IL-13 have been reported to effectively inhibit fibrosis (U.S. Pat. Nos. 6,268,342, 6,303,126, 6,500,835, and 6,664,227).
Age-related macular degeneration (AMD) is the leading cause of blindness in people over 55; and diabetic retinopathy (DR) is the leading cause in people under 55 (Klein, 1994; Williams, 2004). Both diseases are characterized by new blood vessel growth (Freund, 1993; Speicher, 2003; Zarbin, 2004). Macular edema and Diabetic macular edema (DME) occur when fluid and protein deposits collect on or under the macula caused by leaking macular capillaries. Thrombosis of central retinal vein (CRV) and its branches is the second most prevalent vascular pathology after DR, and results in abrupt decrease in visual acuity and is accompanied by macular edema. Thus, anti-angiogenesis treatments are useful in combating all these conditions.
Integrins are heterodimeric transmembrane proteins through which cells attach and communicate with extracellular matrices and other cells. αv integrins are key receptors involved in mediating cell migration and angiogenesis. αv integrins have been shown to be involved in a number of diseases and conditions including ocular angiogenesis and fibrosis of organs. Expression of αv integrins is upregulated in various diseases or conditions, such as AMD and DR, and in mouse model of oxygen-induced retinopathy (OIR) or retinopathy of prematurity (ROP) model (Takagi, 2002). Also, αvβ3 is expressed in new vessels after photocoagulation, but not in normal choroidal vessels, in the laser-induced choroidal neovascularization model for AMD (Kamizuru, 2001). Administration of αv integrins antagonists, such as a cyclic RGD peptide, has been shown to inhibit retinal and choroidal neovascularization (Friedlander, 1996; Chavakis, 2002; Luna, 1996; Riecke, 2001; Yasukawa, 2004). Angiogenesis inhibitors targeting vascular endothelial growth factor (VEGF), other growth factors (e.g., fibroblast growth factor (FGF), platelet-derived growth factor (PDGF)), chemokines (e.g., IL8, SDF1, G-CSF), receptors (e.g., CXCR1, FGF-R, PlGFR, PDGFR, Tie-receptors), intracellular mediators (e.g., c-kit kinase, PI3 kinase, PKC), and extracellular mediators (e.g., integrins, cadherins), as well as inhibitors of pro-angiogenic targets (e.g., phosphoinositide 3 kinase), have been investigated for the treatment of AMD and DR. However, application of these drugs is limited.
Thus, there continues to be a need for compounds, compositions, and methods for treating fibrosis, AMD, DR, DME, and macular edema following retinal vein occlusion, that are safe, effective, and conveniently administered. The present invention addresses the need.